Apache Drill’s cost-based optimizer (CBO) and traditional RDBMS rule-based optimizers differ in their approach to query optimization. CBO uses statistics, such as data distribution and selectivity, to estimate the cost of different execution plans and selects the least expensive one. In contrast, rule-based optimizers rely on a predefined set of rules for transforming queries into more efficient forms.
The advantages of CBO include adaptability to varying data characteristics, better handling of complex queries, and improved performance through accurate plan selection. However, it requires up-to-date statistics and may have higher overhead due to cost calculations. Rule-based optimizers are simpler, with lower overhead, but can be less effective for complex queries or when data characteristics change significantly.
